Comms and Control for Drones
Consumer and commercial drones represent one of the most dynamic areas of embedded design today. Chip, board and system suppliers are offering improved ways for drones to do more processing on board the drone, while also providing solutions for implementing the control and communication subsystems in drones. This article by Circuit Cellar’s Editor-in-Chief Jeff Child looks at the technology and products available today that are advancing the capabilities of today’s drones.

Choosing an MPU/MCU for Industrial DesignBy Microchip Technology’s Jacko Wilbrink
As MCU performance and functionality improve, the traditional boundaries between MCUs and microprocessor units (MPUs) have become less clear. In this article, Jacko examines the changing landscape in MPU vs. MCU capabilities, OS implications and the specifics of new SiP and SOM approaches for simplifying higher-performance computing requirements in industrial applications.

Product Focus: COM Express Boards
The COM Express architecture has found a solid and growing foothold in embedded systems. COM Express boards provide a complete computing core that can be upgraded when needed, leaving the application-specific I/O on the baseboard. This Product Focus section updates readers on this technology and provides a product album of representative COM Express products.

MICROCONTROLLERS ARE DOING EVERYTHING

Connecting USB to Simple MCUsBy Stuart Ball
Sometimes you want to connect a USB device such as a flash drive to a simple microcontroller. Problem is most MCUs cannot function as a USB host. In this article, Stuart steps through the technology and device choices that solve this challenge. He also puts the idea into action via a project that provides this functionality.

Vision System Enables Overlaid ImagesBy Daniel Edens and Elise Weir
In this project article, learn how these two Cornell students designed a system to overlay images from a visible light camera and an infrared camera. They use software running on a PIC32 MCU to interface the two types of cameras. The MCU does the computation to create the overlaid images, and displays them on an LCD screen.

High-Side Current SensingBy Jeff Bachiochi
Jeff says he likes being able to measure things—for example, being able to measure load current so he can predict how long a battery will last. With that in mind, he recently found a high-side current sensing device, Microchip’s EMC1701. In his article, Jeff takes you through the details of the device and how to make use of it in a battery-based system.

Power Analysis Capture with an MCUBy Colin O’Flynn
Low-cost microcontrollers integrate many powerful peripherals in them. You can even perform data capture directly to internal memory. In his article, Colin uses the ChipWhisperer-Nano as a case study in how you might use such features which would otherwise require external programmable logic.

TOOLS AND TECHNIQUES FOR EMBEDDED SYSTEM DESIGN

Easing into the IoT Cloud (Part 2)By Brian Millier
In Part 1 of this article series Brian examined some of the technologies and services available today enabling you to ease into the IoT cloud. Now, in Part 2, he discusses the hardware features of the Particle IoT modules, as well as the circuitry and program code for the project. He also explores the integration of a Raspberry Pi solution with the Particle cloud infrastructure.

Hierarchical Menus for TouchscreensBy Aubrey Kagan
In his December article, Aubrey discussed his efforts to build a display subsystem and GUI for embedded use based on a Noritake touchscreen display. This time he shares how he created a menu system within the constraints of the Noritake graphical display system. He explains how he made good use of Microsoft Excel worksheets as a tool for developing the menu system.

Real Schematics (Part 2)By George Novacek
The first part of this article series on the world of real schematics ended last month with wiring. At high frequencies PCBs suffer from the same parasitic effects as any other type of wiring. You can describe a transmission line as consisting of an infinite number of infinitesimal resistors, inductors and capacitors spread along its entire length. In this article George looks at real schematics from a transmission line perspective.

The December issue of Circuit Cellar magazine is coming soon. Don’t miss this last issue of Circuit Cellar in 2018. Pages and pages of great, in-depth embedded electronics articles prepared for you to enjoy.

Embedded Supercomputing
Gone are the days when supercomputing levels of processing required a huge, rack-based systems in an air-conditioned room. Today, embedded processors, FPGAs and GPUs are able to do AI and machine learning kinds of operation, enable new types of local decision making in embedded systems. In this article, Circuit Cellar’s Editor-in-Chief, Jeff Child, looks at these technology and trends driving embedded supercomputing.

Convolutional Neural Networks in FPGAsDeep learning using convolutional neural networks (CNNs) can offer a robust solution across a wide range of applications and market segments. In this article written for Microsemi, Ted Marena illustrates that, while GPUs can be used to implement CNNs, a better approach, especially in edge applications, is to use FPGAs that are aligned with the application’s specific accuracy and performance requirements as well as the available size, cost and power budget.

NOT-TO-BE-OVERLOOKED ENGINEERING ISSUES AND CHOICES

DC-DC Converters
DC-DC conversion products must juggle a lot of masters to push the limits in power density, voltage range and advanced filtering. Issues like the need to accommodate multi-voltage electronics, operate at wide temperature ranges and serve distributed system requirements all add up to some daunting design challenges. This Product Focus section updates readers on these technology trends and provides a product gallery of representative DC-DC converters.

Real Schematics (Part 1)
Our magazine readers know that each issue of Circuit Cellar has several circuit schematics replete with lots of resistors, capacitors, inductors and wiring. But those passive components don’t behave as expected under all circumstances. In this article, George Novacek takes a deep look at the way these components behave with respect to their operating frequency.

Do you speak JTAG?
While most engineers have heard of JTAG or have even used JTAG, there’s some interesting background and capabilities that are so well know. Robert Lacoste examines the history of JTAG and looks at clever ways to use it, for example, using a cheap JTAG probe to toggle pins on your design, or to read the status of a given I/O without writing a single line of code.

PUTTING THE INTERNET-OF-THINGS TO WORK

Industrial IoT Systems
The Industrial Internet-of-Things (IIoT) is a segment of IoT technology where more severe conditions change the game. Rugged gateways and IIoT edge modules comprise these systems where the extreme temperatures and high vibrations of the factory floor make for a demanding environment. Here, Circuit Cellar’s Editor-in-Chief, Jeff Child, looks at key technology and product drives in the IIoT space.

Internet of Things Security (Part 6)
Continuing on with his article series on IoT security, this time Bob Japenga returns to his efforts to craft a checklist to help us create more secure IoT devices. This time he looks at developing a checklist to evaluate the threats to an IoT device.

Applying WebRTC to the IoT
Web Real-time Communications (WebRTC) is an open-source project created by Google that facilitates peer-to-peer communication directly in the web browser and through mobile applications using application programming interfaces. In her article, Callstats.io’s Allie Mellen shows how IoT device communication can be made easy by using WebRTC. With WebRTC, developers can easily enable devices to communicate securely and reliably through video, audio or data transfer.

WI-FI AND BLUETOOTH IN ACTION

IoT Door Security System Uses Wi-Fi
Learn how three Cornell students, Norman Chen, Ram Vellanki and Giacomo Di Liberto, built an Internet connected door security system that grants the user wireless monitoring and control over the system through a web and mobile application. The article discusses the interfacing of a Microchip PIC32 MCU with the Internet and the application of IoT to a door security system.

Self-Navigating Robots Use BLE
Navigating indoors is a difficult but interesting problem. Learn how these two Cornell students, Jane Du and Jacob Glueck, used Received Signal Strength Indicator (RSSI) of Bluetooth Low Energy (BLE) 4.0 chips to enable wheeled, mobile robots to navigate towards a stationary base station. The robot detects its proximity to the station based on the strength of the signal and moves towards what it believes to be the signal source.

IN-DEPTH PROJECT ARTICLES WITH ALL THE DETAILS

Sun Tracking Project
Most solar panel arrays are either fixed-position, or have a limited field of movement. In this project article, Jeff Bachiochi set out to tackle the challenge of a sun tracking system that can move your solar array to wherever the sun is coming from. Jeff’s project is a closed-loop system using severs, opto encoders and the Microchip PIC18 microcontroller.

Designing a Display System for Embedded Use
In this project article, Aubrey Kagan takes us through the process of developing an embedded system user interface subsystem—including everything from display selection to GUI development to MCU control. For the project he chose a 7” Noritake GT800 LCD color display and a Cypress Semiconductor PSoC5LP MCU.

3D Printing for Embedded Systems
Although 3D printing for prototyping has existed for decades, it’s only in recent years that it’s become a mainstream tool for embedded systems development. Today the ease of use of these systems has reached new levels and the types of materials that can be used continues to expand. This article by Circuit Cellar’s Editor-in-Chief, Jeff Child looks at the technology and products available today that enable 3D printing for embedded systems.

Add GPS to Your Embedded System
We certainly depend on GPS technology a lot these days, and technology advances have brought fairly powerful GPS functionally into our pockets. Today’s miniaturization of GPS receivers enables you to purchase an inexpensive but capable GPS module that you can add to your embedded system designs. In this article, Stuart Ball shows how to do this and take advantage of the GPS functionality.

FCL for Servo Drives
Servo drives are a key part of many factory automation systems. Improving their precision and speed requires attention to fast-current loops and related functions. In his article, Texas Instruments’ Ramesh Ramamoorthy gives an overview of the functional behavior of the servo loops using fast current loop algorithms in terms of bandwidth and phase margin.

FOCUS ON ANALOG AND POWER

Analog and Mixed-Signal ICs
Analog and mixed-signal ICs play important roles in a variety of applications. These applications depend heavily on all kinds of interfacing between real-world analog signals and the digital realm of processing and control. Circuit Cellar’s Editor-in-Chief, Jeff Child, dives into the latest technology trends and product developments in analog and mixed-signal chips.

Sleeping Electronics
Many of today’s electronic devices are never truly “off.” Even when a device is in sleep mode, it draws some amount of power—and drains batteries. Could this power drain be reduced? In this project article, Jeff Bachiochi addresses this question by looking at more efficient ways to for a system to “play dead” and regulate power.

BUILDING CONNECTED SYSTEMS FOR THE IoT EDGE

Easing into the IoT Cloud (Part 1)
There’s a lot of advantages for the control/monitoring of devices to communicate indirectly with the user interface for those devices—using some form of “always-on” server. When this server is something beyond one in your home, it’s called the “cloud.” Today it’s not that difficult to use an external cloud service to act as the “middleman” in your system design. In this article, Brian Millier looks at the technologies and services available today enabling you to ease in to the IoT cloud.

Sensors at the Intelligent IoT Edge
A new breed of intelligent sensors has emerged aimed squarely at IoT edge subsystems. In this article, Mentor Graphics’ Greg Lebsack explores what defines a sensor as intelligent and steps through the unique design flow issues that surround these kinds of devices.

FUN AND INTERESTING PROJECT ARTICLES

MCU-Based Project Enhances Dance Game
Microcontrollers are perfect for systems that need to process analog signals such as audio and do real-time digital control in conjunction with those signals. Along just those lines, learn how two Cornell students Michael Solomentsev and Drew Dunne recreated the classic arcade game “Dance Dance Revolution” using a Microchip Technology PIC32 MCU. Their version performs wavelet transforms to detect beats from an audio signal to synthesize dance move instructions in real-time without preprocessing.

Building an Autopilot Robot (Part 2)
In part 1 of this two-part article series, Pedro Bertoleti laid the groundwork for his autopiloted four-wheeled robot project by exploring the concept of speed estimation and speed control. In part 2, he dives into the actual building of the robot. The project provides insight to the control and sensing functions of autonomous electrical vehicles.

… AND MORE FROM OUR EXPERT COLUMNISTS

Embedded System Security: Live from Las Vegas
This month Colin O’Flynn summarizes a few interesting presentations from the Black Hat conference in Las Vegas. He walks you through some attacks on bitcoin wallets, x86 backdoors and side channel analysis work—these and other interesting presentations from Black Hat.

Highly Accelerated Product Testing
It’s a fact of life that every electronic system eventually fails. Manufacturers use various methods to weed out most of the initial failures before shipping their product. In this article, George Novacek discusses engineering attempts to bring some predictability into the reliability and life expectancy of electronic systems. In particular, he focuses on Highly Accelerated Lifetime Testing (HALT) and Highly Accelerated Stress Screening (HASS).

STMicroelectronics has released the STSPIN830 and STSPIN840 single-chip drivers that simplify the design of low-to-mid-power motor controls in the 7 V to 45 V range. The devices contain flexible control logic and low-RDS(ON) power switches for industrial applications, medical technology, and home appliances.The STSPIN830 for driving 3-phase brushless DC motors has a mode-setting pin that lets users control the three half bridges of the integrated power stage with direct U, V, and W pulse-width modulated (PWM) inputs, or by applying signals to each gate individually for higher control flexibility. A dedicated sense pin for each inverter leg simplifies setting up three-shunt or single-shunt current sensing for Field-Oriented Control (FOC).

The STSPIN840 can drive two brushed DC motors or one larger motor leveraging ST’s well- known, market-proven paralleling concept, which allows the integrated full bridges to be configured as two separate bridges or as a single bridge using the two sets of MOSFETs in parallel for lower RDS(ON) and higher current rating.

The integrated power stage of each device features ST-proprietary MOSFETs with low RDS(ON) of only 500 mΩ to combine high efficiency with economy. The option to use the output bridges individually or connected in parallel, in the STSPIN840, helps trim the BOM for multi-motor applications.

With their high feature integration and flexibility, the drivers enable more compact and cost-effective controls for industrial, robotic, medical, building-automation, and office-equipment applications. The STSPIN830 is ideal for factory-automation end-points, home appliances, small pumps, and fans for computer or general-purpose cooling. The STSPIN840 targets ATM and money-handling machines, multi-axis stage-lighting mechanisms, thermal printers, textile or sewing machines, and vending machines.

The STSPIN830 and STSPIN840 are both in production now, as 4 mm x 4 mm QFN devices. Pricing for both starts from $1.25 for orders of 1,000 pieces.

Two STM32 Nucleo expansion boards are provided to facilitate product evaluation and build functional prototypes using the STM32 Open Development Environment: X-NUCLEO-IHM16M1 for the STSPIN830 and X-NUCLEO-IHM15A1 for the STSPIN840, both priced at $16.

Motion Control for Robotics
Motion control technology for robotic systems continues to advance, as chip- and board-level solutions evolve to meet new demands. These involve a blending of precise analog technologies to control position, torque and speed with signal processing to enable accurate, real-time motor control. Here, Circuit Cellar’s Editor-in-Chief, Jeff Child, looks the latest technology and product advances in motion control for robotics.

Electronic Speed Control (Part 3)
Radio-controlled drones are one among many applications that depend on the use of an Electronic Speed Controller (ESC) as part of its motor control design. After observing the operation of a number of ESC modules, in this part Jeff Bachiochi focuses in more closely on the interaction of the ESC with the BLDC motor.

BUILDING CONNECTED SYSTEMS

Product Focus: IoT Gateways
IoT gateways are a smart choice to facilitate bidirectional communication between IoT field devices and the cloud. Gateways also provide local processing and storage capabilities for offline services as well as near real-time management and control of edge devices. This Product Focus section updates readers on these technology trends and provides a product gallery of representative IoT gateways.

Wireless Weather Station
Integrating wireless technologies into embedded systems has become much easier these days. In this project article, Raul Alvarez Torrico describes his home-made wireless weather station that monitors ambient temperature, relative humidity, wind speed and wind direction, using Arduino and a pair of cheap Amplitude Shift Keying (ASK) radio modules.

FOCUS ON ANALOG AND POWER TECHNOLOGY

Frequency Modulated DDS
Prompted by a reader’s query, Ed became aware that you can no longer get crystal oscillator modules tuned to specific frequencies. With that in mind, Ed set out to build a “Channel Element” replacement around a Teensy 3.6 board and a DDS module. In this article, Ed Nisley explains how the Teensy’s 32-bit datapath and 180 MHz CPU clock affect the DDS frequency calculations. He then explores some detailed timings.

Power Supplies / Batteries
Sometimes power decisions are left as an afterthought in system designs. But your choice of power supply or battery strategy can have a major impact on your system’s capabilities. Circuit Cellar’s Editor-in-Chief, Jeff Child, dives into the latest technology trends and product developments in power supplies and batteries.

Murphy’s Laws in the DSP World (Part 3)
Unpredictable issues crop up when you move from the real world of analog signals and enter the world of digital signal processing (DSP). In Part 3 of this article series, Mike Smith and Mai Tanaka focuses on strategies for how to—or how to try to—avoid Murphy’s Laws when doing DSP.

SYSTEM DESIGN ISSUES IN VIDEO AND IMAGING

Virtual Emulation for Drones
Drone system designers are integrating high-definition video and other features into their SoCs. Verifying the video capture circuitry, data collection components and UHD-4K streaming video capabilities found in drones is not trivial. In his article, Mentor’s Richard Pugh explains why drone verification is a natural fit for hardware emulation because emulation is very efficient at handling large amounts of streamed data.

LIDAR 3D Imaging on a Budget
Demand is on the rise for 3D image data for use in a variety of applications, from autonomous cars to military base security. That has spurred research into high precision LIDAR systems capable of creating extremely clear 3D images to meet this demand. Learn how Cornell student Chris Graef leveraged inexpensive LIDAR sensors to build a 3D imaging system all within a budget of around $200.

AND MORE FROM OUR EXPERT COLUMNISTS

Velocity and Speed Sensors
Automatic systems require real-life physical attributes to be measured and converted to electrical quantities ready for electronic processing. Velocity is one such attribute. In this article, George Novacek steps through the math, science and technology behind measuring velocity and the sensors used for such measurements.

Recreating the LPC Code Protection Bypass
Microcontroller fuse bits are used to protect code from being read out. How well do they work in practice? Some of them have been recently broken. In this article Colin O’Flynn takes you through the details of such an attack to help you understand the realistic threat model.

FPGA System Design
Long gone now are the days when FPGAs were thought of as simple programmable circuitry for interfacing and glue logic. Today, FPGAs are powerful system chips with on-chip processors, signal processing functionality and rich offerings or high-speed connectivity. Here, Circuit Cellar’s Editor-in-Chief, Jeff Child, looks at the latest technology and trends in FPGA system design.

Managing FPGA Design Complexity
Modern FPGAs can contain millions of logic gates and thousands of embedded DSP processors allowing FPGA hardware designers to create extremely sophisticated and complex application-specific hardware functions. In this article, Pentek’s Bob Sgandurra explores how today’s FPGA technology has revamped the roles of both hardware and software engineers as well as how dealing with on-chip IP adds new layers of complexity.

HIGH-INTEGRATION AT THE CHIP-AND BOARD-LEVEL

Product Focus: Small and Tiny Embedded BoardsAn amazing amount of computing functionality can be squeezed on to a small form factor board these days. These company—and even tiny—board-level products meet the needs of applications where extremely low SWaP (size, weight and power) beats all other demands. This Product Focus section updates readers on this technology trend and provides a product album of representative small and tiny embedded boards.

Microcontrollers and Processors
Today’s crop of microcontrollers and embedded processors provide a rich continuum of features, functions and capabilities. It’s hard to tell anymore where the dividing line is, especially when a lot of them use the same CPU cores. Circuit Cellar’s Editor-in-Chief, Jeff Child, delves into the technology and product trends of MCUs and embedded processors.

CAN’T STOP THE SIGNAL

Murphy’s Laws in the DSP World (Part 2)
Many unexpected issues come into play when you move from the real world of analog signals and enter the world of digital signal processing (DSP). Part 2 of this article series by Michael Smith, Mai Tanaka and Ehsan Shahrabi Farahani charges forward introducing “Murphy’s Laws of DSP” #7, #8 and #9 and looks at the spectral analysis of DSP signals.

Signature Analyzer Uses NXP MCU
Doing a signature analysis of a signal used to require an oscilloscope to display your results. In this article, Brian Millier shows how you can build a free-standing tester that uses mostly just the internal peripherals of an NXP ARM microcontroller. He described how the tester operates and how he implemented it using a Teensy 3.5 development module and an intelligent 4.3-inch TFT touch-screen display.

Pitfalls of Filtering Pulsed Signals
Filtering pulsed signals can be a tricky prospect. Using a recent customer implementation as an example, Robert Lacoste highlights various alternative approaches and describes the key concepts involved. Simulation results are provided to help readers understand what’s going on.

PROJECT-BASED STORIES WITH ALL THE DETAILS

Electronic Speed Control (Part 2)
In Part 1, Jeff Bachiochi discussed the mechanical differences between DC brushed and brushless DC (BLDC) motors. This time he dives into basics of an Electronic Speed Controller’s operations and its circuitry. And all this is illustrated via his ESC-based project that uses a Microchip PIC MCU.

Build an Audio Response Light Display
Light shows have been a part of entertainment situations seemingly forever, but the technology has evolved over time. These light shows have their origin in the primitive “light organs” of the 1960s in which each spectral band had its own color that pulsed in intensity with audio amplitudes within its range of frequencies. In this article, Devlin Gualtieri discusses his circuit design that implements a light organ using today’s IC and LED technologies.

AND MORE FROM OUR EXPERT COLUMNISTS

Internet of Things Security (Part 4)
In this next part of his article series on IoT security, Bob Japenga looks at how checklists and the common criteria framework can help us create more secure IoT devices. He covers how to create a list of security assets and to establish threat checklists that identify all the threats to your security assets.

Thermoelectric Cooling (Part 2)
In Part 1 George Novacek described how he built a test chamber using some electronics combined with components salvaged from his thermoelectric water cooler. To confirm his test results, he purchased another thermoelectric cooler and repeated the tests. In Part 2 he covers the results of these tests along with some theoretical performance calculations.

Today’s small fans and blowers depend on brushless DC (BLDC) motor technology for their operation. Here, Ed explains how these seemingly simple devices are actually quite complex when you measure them in action.

By Ed Nisley

The 3D printer Cambrian Explosion unleashed both the stepper motors you’ve seen in previous articles and the cooling fans required to compensate for their abuse. As fans became small and cheap, Moore’s Law converted them from simple DC motors into electronic devices, simultaneously invalidating the assumptions people (including myself) have about their proper use.

In this article, I’ll make some measurements on the motor inside a tangential blower and explore how the data relates to the basic physics of moving air.

Brushless DC Motors

Electric motors, regardless of their power source, produce motion by opposing the magnetic field in their rotor against the field in their stator. Small motors generally produce one magnetic field with permanent magnets, which means the other magnetic field must change with time in order to keep the rotor spinning. Motors powered from an AC source, typically the power line for simple motors, have inherently time-varying currents, but motors connected to a DC source require a switching mechanism, called a commutator, to produce the proper current waveforms.

Mechanical commutators date back to the earliest days of motor technology, when motors passed DC power supply current through graphite blocks sliding over copper bars to switch the rotor winding currents without external hardware. For example, the commutator in the lead photo switches the rotor current of a 1065 horsepower marine propulsion motor installed on Fireboat Harvey in 1930, where it’s still in use after nine decades.

Fireboat Harvey’s motors produce the stator field using DC electromagnets powered by steam-driven exciter generators. Small DC motors now use high-flux, rare-earth magnets and no longer need boilers or exhaust stacks.

Although graphite sliding on copper sufficed for the first century of DC motors, many DC motors now use electronic commutation, with semiconductor power switches driven by surprisingly complex logic embedded in a dedicated controller. These motors seem “inside out” compared to older designs, with permanent magnets producing a fixed rotor field and the controller producing a time-varying stator field. The relentless application of Moore’s Law put the controller and power switches on a single PCB hidden inside the motor case, out of sight and out of mind.

Because semiconductor switches eliminated the need for carbon brushes, the motors became known as Brushless DC motors. Externally, they operate from a DC supply and, with only two wires, don’t seem particularly complicated. Internally, their wiring and currents resemble multi-phase AC induction motors using pseudo-sinusoidal stator voltage waveforms. As a result, they have entirely different power supply requirements.

The magnetic field in the rotor of a mechanically commutated motor has a fixed relationship to the stator field. As the rotor turns, its magnetic field remains stationary with respect to the stator as the brushes activate successive sections of the rotor winding to produce essentially constant torque against the stator field. Electronically commutated motors must sense the rotor position to produce stator currents with the proper torque against the moving rotor field. As you’ll see, the motor controller can use the back EMF generated by the spinning rotor to determine its position, thereby eliminating any additional components.

Figure 1The blower motor current varies linearly with its supply voltage, so the power consumption varies as the square of the voltage. The motor speed depends on the balance between torque and load.

I originally thought Brushless DC (BLDC) motors operated much like steppers, with the controller regulating the winding current, but the switches actually regulate the voltage applied to the windings, with the current determined by the difference between the applied voltage and the back EMF due to the rotor speed. The difference between current drive and voltage drive means steppers and BLDC motors have completely different behaviors.

Constant Voltage Operation

The orange trace along the bottom of Figure 1 shows the current drawn by the 24 V tangential blower shown in Figure 2, without the anemometer on its outlet, for supply voltages between 2.3 V and 26 V. The BLDC motor controller shapes the DC supply voltage into AC waveforms, the winding current varies linearly with the applied voltage and, perhaps surprisingly, the blower looks like a 100 Ω resistor.

Figure 2An anemometer measures the blower’s outlet air speed and a square of retroreflective tape on the rotor provides a target for the laser tachometer. If you are doing this in a lab, you should build a larger duct with a flow straightener and airtight joints.

The blower’s power dissipation therefore varies as the square of the supply voltage, as shown by the calculated dots in the purple curve. In fact, the quadratic equation fitting the data has 0.00 coefficients for both the linear and constant terms, so it’s as good as simple measurements can get.

As you saw in March (Circuit Cellar #332) and May (Circuit Cellar #334), a stepper motor driven by a microstepping controller has a constant winding current and operates at a constant power. Increasing the supply voltage increases the rate of current change but, because the controller applies the increasing voltage with a lower duty cycle, it doesn’t directly increase power dissipation. …

Note: We’ve made the October 2017 issue of Circuit Cellar available as a free sample issue. In it, you’ll find a rich variety of the kinds of articles and information that exemplify a typical issue of the current magazine.

Wireless Standards and Solutions for IoT
One of the critical enabling technologies making the Internet-of-Things possible is the set of well-established wireless standards that allow movement of data to and from low-power edge devices. Here, Circuit Cellar’s Editor-in-Chief, Jeff Child, looks at key wireless standards and solutions playing a role in IoT.

Product Focus: IoT Device Modules
The rapidly growing IoT phenomenon is driving demand for highly integrated modules designed to interface with IoT devices. This Product Focus section updates readers on this technology trend and provides a product album of representative IoT interface modules.

TOOLS AND TECHNIQUES AT THE DESIGN PHASE

EMC Analysis During PCB Layout
If your electronic product design fails EMC compliance testing for its target market, that product can’t be sold. That’s why EMC analysis is such an important step. In his article, Mentor Graphics’ Craig Armenti shows how implementing EMC analysis during the design phase provides an opportunity to avoid failing EMC compliance testing after fabrication.

Extreme Low-Power Design
Wearable consumer devices, IoT sensors and handheld systems are just a few of the applications that strive for extreme low-power consumption. Beyond just battery-driven designs, today’s system developers want no-battery solutions and even energy harvesting. Circuit Cellar’s Editor-in-Chief, Jeff Child, dives into the latest technology trends and product developments in extreme low power.

Op Amp Design Techniques
Op amps can play useful roles in circuit designs linking the real analog world to microcontrollers. Stuart Ball shares techniques for using op amps and related devices like comparators to optimize your designs and improve precision.

Wire Wrapping Revisited
Wire wrapping may seem old fashioned, but this tried and true technology can solve some tricky problems that arise when you try to interconnect different kinds of modules like Arduino, Raspberry Pi and so on. Wolfgang Matthes steps through how to best employ wire wrapping for this purpose and provides application examples.

DEEP DIVES ON MOTOR CONTROL AND MONITORING

BLDC Fan Current
Today’s small fans and blowers depend on brushless DC (BLDC) motor technology for their operation. In this article, Ed Nisley explains how these seemingly simple devices are actually quite complex when you measure them in action. He makes some measurements on the motor inside a tangential blower and explores how the data relates to the basic physics of moving air.

Electronic Speed Control (Part 1)
An Electronic Speed Controller (ESC) is an important device in motor control designs, especially in the world of radio-controlled (RC) model vehicles. In Part 1, Jeff Bachiochi lays the groundwork by discussing the evolution of brushed motors to brushless motors. He then explores in detail the role ESC devices play in RC vehicle motors.

MCU-Based Motor Condition Monitoring
Thanks to advances in microcontrollers and sensors, it’s now possible to electronically monitor aspects of a motor’s condition, like current consumption, pressure and vibration. In this article, Texas Instrument’s Amit Ashara steps through how to best use the resources on an MCU to preform condition monitoring on motors. He looks at the signal chain, connectivity issues and A-D conversion.

AND MORE FROM OUR EXPERT COLUMNISTS

Verifying Code Readout Protection Claims
How do you verify the security of microcontrollers? MCU manufacturers often make big claims, but sometimes it is in your best interest to verify them yourself. In this article, Colin O’Flynn discusses a few threats against code readout and looks at verifying some of those claimed levels.

Thermoelectric Cooling (Part 1)
When his thermoelectric water color died prematurely, George Novacek was curious whether it was a defective unit or a design problem. With that in mind, he decided to create a test chamber using some electronics combined with components salvaged from the water cooler. His tests provide some interesting insights into thermoelectric cooling.